Variable geometry slip ring assembly permitting variation in characteristic impedance or tuning



Aug. 25, 1964 P. A. FILIPCZAK 3,146,411

VARIABLE GEOMETRY SLIP RING ASSEMBLY PERMITTING VARIATION IN CHARACTERISTIC IMPEDANCE 0R TUNING Filed June 27, 1962 2 Sheets-Sheet 1 INVENTOR. PETER Fh/Pc ZHK,

ATTORNEY Aug. 25, 1964 P. A. FILIPCZAK VARIABLE GEOMETRY SLIP RING ASSEMBLY PERMITTING VARIATION IN CHARACTERISTIC IMPEDANCE OR TUNING 2 Sheets-Sheet 2 INVEN TOR.

Filed June 27, 1962 K m .T

United States Patent 3,146,411 VARIABLE GEOMETRY SLIP RING ASSEMBLY PERMITTING VARIATION IN CHARACTERISTIC IMPEDANCE OR TUNING Peter A. Filipczalr, Pararnus, N.J., assignor to Electro- Tec Corp., West Caldwell, NJ., a corporation of New Jersey Filed June 27, 1962, Ser. No. 205,774 7 Claims. (Cl. 33324) This invention relates in general to slip rings of the type that include two parts that are relatively rotatable about a common axis, one of which carries a plurality of conductor rings while the other carries a brush element for each conductor ring.

Measurements on high frequency type slip rings have indicated that a slip ring of this general nature used as a rotary coupling tends to resemble a lumped circuit element in the high frequency range. Since the lumped device looks like an RLC network, it is desirable to design a slip ring that will vary one of these parameters.

The slip ring is usually designed to match the characteristic impedance of the electrical supply cable that is used with the ring according to a formula, and a primary object of the invention is to provide a slip ring which shall be constructed in a novel and improved manner to vary the capacitance (C) and inductance (L) values in order to approach the desired circuit parameters.

It is well known that to lower the capacitive coupling in a coaxial circuit, the material having the ability to absorb the'minimum amount of energy, for example, a low dielectric constant material, must be selected. The most desirable condition, of course, would be to suspend the adjacent conductor rings of a slip ring assembly in air with a dielectric constant of one. This is a general practice which is used in the construction of low loss coaxial transmission lines in which the inner conductor is supported within the outer conductor on insulating beads of flexible solid dielectric such as polyethylene.

Another object of the invention is to provide a novel and improved construction and combination of a conducting ring, a support therefor and dielectric material which will simulate the condition above described in the coaxial transmission lines, that is, to keep the cross sectional area of the conducting ring to a minimum and to minimize the amount of dielectric material between the conducting ring and a shield support frame therefor.

Stillanother object of the invention is to provide a slip ring of this character wherein the inductance and capacitance values shall be variable by means of a sectional inductance-capacitance varying member for each conductor ring, the sections of which are movable toward and away from the conductor ring.

A further object is to provide an optimum slip ring assembly of the character described which shall permit easy, quick and accurate variation of the inductance and capacitance values for use with a known transmission line and shall also provide means for; tuning a-circuit over a variable bandwidth so that the designer of the slip ring shall have a broader scope of variation of circuit characteristics than has been heretofore possible.

, Other objects, advantages and results of the invention will be brought out by the following description in conjunctionwith the accompanying drawings in which FIGURE 1 is a front elevation of a slip ring assembly embodying the invention with portions broken away and shown in section on two different planes perpendicular to the axis of the assembly;

FIGURE 1A is a fragmentary sectional view approximately on the plane of the line 1A1A of FIGURE 1;

FIGURE 2 is a side elevation taken approximately from the line 22 of FIGURE 1;

FiGURE 3 is a greatly enlarged fragmentary sectional view on an axial plane of the assembly with portions shown in side elevation; and

FIGURE 4 is an enlarged portion of FIGURE 1 included between the dot-and-dash lines denoted 44.

Specifically describing the illustrated embodiment of the invention, the slip ring assembly has been shown as comprising two relatively rotatable coaxial parts A and B, both of which may be rotatable or either one of which may be stationarily mounted. As shown, the inner section A is tubular and circular in cross section so that it a may be telescopically fitted upon a shaft C or other suitable support while the outer section B is ring-like and encircles the inner section A. Preferably the outer section is rotatably mounted on the inner section by antifriction bearings D. Both sections are approximately L- shaped in cross section, the outer section having a circumferential portion E and an inwardly extending end flange F, while the inner section has a circumferential portion G and an end flange H that is separably secured to one end of the circumferential portion by suitable means such as cap screws 1. The two sections thus provide between them a circumferential space in which are mounted the conductor rings and their supporting elements. As shown, the outer periphery of the circumferential portion of the inner section has a plurality of longitudinal grooves in each of which is secured a rail or block of dielectric material 2, said blocks being preferably spaced equidistantly circumferentially of the section as best shown in FIGURE 1. A plurality of annular shield-support frames I, one for each conductor ring, are tightly mounted on said rails in spaced relation along the axis of the section as best shown in FIGURE 3. Each frame is preferably formed of nonmagnetic material such as aluminum, to provide a shield against electromagnetism, and has a circumferential portion 3 and end flanges 4 and 5, one of which, in the present instance, the flange 5, is separably connected to the circumferential portion 3 as by screws 6.

Mounted on the circumferential portion 3 of each support frame and between the flanges 4'and 5 thereof is a ring 7 of dielectric material in the outer circumference of which is a conductor ring 8 that is preferably electro-deposited. The sides of the dielectric ring are preferably cut away as indicated at 9 and the inner periphery of the dielectric ring is cut away at 10 so as to provide a minimum of contact of the dielectric material with the shieldsupport frames I. Dielectric buttons 11 equidistantly spaced circumferentially of the support frames, hold the support frames in spaced insulated relation to each other and similar buttons 12 are interposed between the endmost support frame and the end flange H of the inner section A of the assembly so that said flange serves to clamp the support rings in position with the support frame opposite the flange H abutting circumferential flanges 13 on the dielectric blocks 2.

Preferably, the removable flanges 5 are formed of copper or brass 'and have on their outer peripheries electrodeposited layers 14 of conducting material such as silver with which cooperate brushes 15 for grounding the assembly as will be hereinafter described.

Coacting with each of the conductor rings 8 is a brush 16 that is mounted in a brush block K formed of low loss dielectric material and secured to the outer periphery of the outer section of the assembly in any suitable manner as by cap screws 17. Connected to these brush blocks in the usual manner is a known type of coaxial cable coupling L that has a metal sheath a part of which is a metal flange 19 which is connected to the brush block by screws 20 one of which, denoted 21, is long enough to extend I 3 through the brush block and serve also to connect the brush to the brush block. The brush 15 is shown as formed of a U-shaped leaf spring having its base portion secured to the brush block and its arms resiliently engaging the corresponding ground ring or flange 5.

The main brush 16 is normally pressed by a spring 16a into contact with the corresponding conductor ring 8 and is electrically connected by an electrical conductor 22 to the coaxialcable.

As shown, for compactness and convenience in construction, the brush blocks for all of the rings are disposed in a common axial plane of the assembly with the brush block for the intermediate conductor ring disposed at 180 degrees to the brush blocks for the other conductor rings.

An important feature of the invention is an inductancecapacitance varying member M for each conductor ring 8, which is shown as comprising a plurality of identical arcuate sections 23, in the present instance four sections, each of a length of somewhat less than 90 degrees and interposed between the circumferential flange E of the outer assembly section B and the corresponding conductor ring. Each member M is arranged in a groove 24 in the outer assembly section. The adjacent sections 23 are spaced apart at their ends, and the brush block for the corresponding conductor ring is disposed in the space between the ends of two adjacent sections as best shown in FIGURE 1. The two end surfaces of each section are shown as parallel to a common axial plane of the assembly. In eachspace between the ends of the other sections is disposed a bridge block 25 of a size and shape to constitute in effect a continuation of the sections 23 as best shown in, FIGURE 4, the bridge block being fixedly secured to the outer section as by cap screw 26 threaded in a dielectric bushing 26a, and preferably having a pin 27 projecting from each end thereof and spring pressed into contact with the end of the adjacent section 23 by a spring 27a. Preferably, a layer 28 of dielectric material is interposed between each member M and the circumferential portion of the outer assembly section, and dielectric rings 28a. are disposed-between said member and the side walls of the corresponding grooves 24.

Each section 23 is slidably mounted on the outer assembly section by guide pins 29, one adjacent each end of the section and parallel to the other pin and to a common axialplane of the assembly. Preferably the pins are insulated fromthe assembly section and the section 23 by dielectric sleeves 29a.

In accordance with the invention the sections 23 are independently movabletoward and away from the corresponding conductor ring, and for this purpose is shown an adjusting screw 30. for each section, said screw being threaded in a dielectirc bushing 31 in the outer assembly section and having a thumb piece 32 at one end and a jam nut 33 for holding the screw in adjusted positions. The inner end of the screw extends into an opening 34 in the corresponding section 23 and has a circumferential groove 35 in which is disposed a pin 36 that is secured in the section 23 and -is perpendicular to the axis of the screw. There is thus a swivel connection between the screw and the section 23 of the inductance-capacitance varying member M so'that upon .rotation of the screw, the corresponding section 23 can be minutely adjusted relatively to the conductor ring 8-. Preferably the thumb piece 32 will have graduationsthereon with which coact a pointer 37 secured on the outer periphery of the assembly section B.

The conductor rings 8 may be connected incircuit with a transmission line in any suitable manner for example by a coupling 39 of known construction which has a con- .ductor 40 that extends through the dielectric ring 7 into From the foregoing, it will be understood that during operation of the slip ring assembly, the electricity will be conducted from or to each line wire 41 through the conducting ring 8 and the corresponding brush 16 to or from the corresponding coaxial cable L. The conductor ring 8 having been designated to match the characteristic impedance of the cable, the inductance and capacitance values can be varied by proper adjustment of the sections 23 of the inductance-capacitance varying member through rotation of the corresponding screws 30. Thus a slip ring assembly can be adapted for use with a known transmission line by simply adjusting the sections 23 of the inductance-capacitance varying member M; and the scope aiforded the designer of the assembly in establishing his circuit characteristics is correspondingly broadened 'beyond what has been possible heretofore.

The invention also permits the conductor ring to be kept at a minimum cross sectional area so that it will have a capacitance per foot equal to or lower than that of the cable being used, and the construction reduces to the minimum the contact between the dielectric and the mag neticshield support frames so as toreduce the capacitance, coupling between the two elements. All of these functional advantages are achieved with a simple and relatively inexpensive construction.

I claim:

1. A high frequency slip ring assembly comprising relatively rotatable inner and outer sections operating as a portion of a high frequency transmission line with a variable geometry, the rotatable and non-rotatable sections being comprised of elements whose capacitance and inductance characteristics are so arranged as to result in a characteristic impedance (inductance-capacitance ratio) to match that of the attendant transmission line, the inner section having an annular part and the outer section having an annular part in encircling relation to the annular part of the inner section, a conductor ring mounted on said inner section in coaxial insulated relation thereto, a brush mounted on the outer section in insulated relation thereto and in frictional contact with conductor ring, a portion of said outer section comprising separate members movable relatively to said conductor ring such that the capacitance between said conductor ring and, said separate members may be varied, thus varying the characteristic impedance (inductance-capacitance ratio) of the system.

2. A variable geometry slip ring assembly as defined in claim 1 with the addition of a shield for said conductor ring formed of non-magnetic material, and means for grounding said shield.

3. A variable geometry slip ring assembly as defined in claim 1 wherein said portion of the outer section comprises a plurality of arcuate sections of the same radius in spaced juxtaposition to and concentric with said conductor ring, and with the addition of means for adjusting each of said sections of said portion of the outer section toward and away from said conductor ring.

4. A variable geometry slip ring assembly as defined in claim 1 wherein said portion of the outer section comprises a plurality of arcuate sections, the inner arcuate surfaces of said sections of the inductance-capacitance varying member being juxtaposed to the outer peripheral surface of said conductor ring and being concentric therewith when in one position, and with addition of means for adjusting each of said sections'of said portion of the outer section toward and away from said conductor ring.

' 5. A variable geometry slip ring assembly comprising part of the inner section, a plurality of conductor rings mounted on said inner section coaxial with said section and in spaced relation to each other along the axis of V the section and insulated from each other and from said inner section, a brush for each conductor ring mounted on said outer section in insulated relation thereto, and an inductance-capacitance varying member for each conductor ring comprising a plurality of arcuate sections mounted on said outer section of the assembly for movement toward and from the conductor rings, and means for so moving said section of said inductance-capacitance varying member.

6. A variable geometry slip ring assembly comprising an inner section and an outer section each including an annular part rotatable coaxially with and relatively to the annular part of the other section, a dielectric ring having a conductor ring concentrically disposed thereon, an annular shield-support frame of non-magnetic material mounted on the annular part of the inner section in insulated relation thereto and carrying said dielectric ring, a brush mounted on said annular part of the outer section and insulated therefrom and in contact with said conductor ring, means for grounding said shield-support frame, means connecting said brush to a circuit wire, means connecting said conductor ring to another circuit wire, and an inductance-capacitance varying member mounted on and insulated from said outer section in spaced juxtaposition to said conductor ring and for movement relatively thereto, said conductor ring being mounted on the outer periphery of said dielectric ring, and said inductance-capacitance varying member comprising a plurality of arcuate sections in spaced juxtaposition to and concentric with said conductor ring, said sections being in spaced end to end relation to each other and there being guide means spaced lengthwise of each section and parallel to a common axial plane of said assembly, for movement of said sections toward and from said conductor ring, and means for so moving each section of said member.

7. A variable geometry slip ring assembly comprising an inner section and an outer section each including an annular part rotatable coaxially with and relatively to the annular part of the other section, a dielectric ring having a conductor ring concentrically disposed thereon, an annular shield-support frame of non-magnetic material mounted on the annular part of the inner section in insulated relation thereto and carrying said dielectric ring, a brush mounted on said annular part of the outer section and insulated therefrom and in contact with said conductor ring, means for grounding said shield-support frame, means connecting said brush to a circuit wire,-

means connecting said conductor ring to another circuit wire, and an inductance-capacitance varying member mounted on and insulated from said outer section in spaced juxtaposition to said conductor ring and for movement relatively thereto, said conductor ring being mounted on the outer periphery of said dielectric ring, and said inductance-capacitance varying member comprising a plurality of arcuate sections in spaced juxtaposition to and concentric with said conductor ring, said sections being in spaced end to end relation to each other and there being guide means for movement of each section toward and from said conductor ring, the brush for each conductor being located in one of the spaces between said sections of the inductance-capacitance varying member, and there being a bridge block in each of the other said spaces secured to said outer section of the assembly and yielding means for maintaining conductive paths between said bridge blocks and the adjacent sections of said inductance-capacitance varying member.

References Cited in the file of this patent UNITED STATES PATENTS 2,445,793 Marchand July 27, 1948 2,605,357 Salisbury July 29, 1952 2,749,524 De Rosa et al June 5, 1956 2,945,193 Strom July 12, 1960 3,064,212 Alford Nov. 13, 1962 

1. A HIGH FREQUENCY SLIP RING ASSEMBLY COMPRISING RELATIVELY ROTATABLE INNER AND OUTER SECTIONS OPERATING AS A PORTION OF A HIGH FREQUENCY TRANSMISSION LINE WITH A VARIABLE GEOMETRY, THE ROTATABLE AND NON-ROTATABLE SECTIONS BEING COMPRISED OF ELEMENTS WHOSE CAPACITANCE AND INDUCTANCE CHARACTERISTICS ARE SO ARRANGED AS TO RESULT IN CHARACTERISTIC IMPEDANCE (INDUCTANCE-CAPACITANCE RATIO) TO MATCH THAT OF THE ATTENDANT TRANSMISSION LINE, THE INNER SECTION HAVING AN ANNULAR PART AND THE OUTER SECTION HAVING AN ANNULAR PART IN ENCIRCLING RELATION TO THE ANNULAR PART OF THE INNER SECTION, A CONDUCTOR RING MOUNTED ON SAID INNER SECTION IN COAXIAL INSULATED RELATION THERETO, A BRUSH MOUNTED ON THE OUTER SECTION IN INSULATED RELATION THERETO AND IN FRICTIONAL CONTACT WITH CONDUCTOR RING, A PORTION OF SAID OUTER SECTION COMPRISING SEPARATE MEMBERS MOVABLE RELATIVELY TO SAID CONDUCTOR RING SUCH THAT THE CAPACITANCE BETWEEN SAID CONDUCTOR RING AND SAID SEPARATE MEMBERS MAY BE VARIED, THUS VARYING THE CHARACTERISTIC IMPEDANCE (INDUCTANCE-CAPACITANCE RATIO) OF THE SYSTEM. 